Kouji Suzuki

Multi-field driving method for reducing LCD power consumption

We have developed a multi-field driving method for TFT-LCDs in which a displayed image was divided into at least three interlaced sub-field images where visible flicker did not occur as the image refresh rate was decreased. This method made it possible not only to reduce driving-power consumption in the case of still images to less than half, compared to that of conventional methods, but also to ensure that large-area flicker and line flicker were invisible to the human eye.

Accurate Calibration Line for Super-Precise Coefficient of Thermal Expansion Evaluation Technology of TiO2-Doped SiO2 Ultra-Low-Expansion Glass Using the Line-Focus-Beam Ultrasonic Material Characterization System

We obtained an accurate relationship between the leaky surface acoustic wave (LSAW) velocities and TiO2 concentrations. Such a relationship is needed for the line-focus-beam ultrasonic material characterization (LFB-UMC) system as a new technology for evaluating the coefficient of thermal expansion (CTE) of ultra-low-expansion glasses with extremely high precision. Using commercially available TiO2–SiO2 glass with periodic striae, averaged velocities for LSAW propagation parallel to the striae plane at 225 MHz and averaged TiO2 concentrations by X-ray fluorescence analysis were measured on the surface of seven specimen substrates prepared perpendicular to the striae plane. The obtained sensitivity of LSAW velocity to TiO2 concentration was -0.0601 wt %/(m/s), and the measurement resolution was estimated to be ±0.0084 wt % for ±2 σ (σ: standard deviation) from the LSAW velocity measurement resolution of ±0.14 m/s. The TiO2 concentration for the standard TiO2–SiO2 glass specimen with a LSAW velocity of 3308.18 m/s for system calibration was determined to be 7.09 wt %. This ultrasonic technology will contribute greatly to the development of the ultra-low-expansion glasses needed for extreme ultraviolet lithography (EUVL) systems.

A back‐side passivation film on a‐Si:H thin film transistor

Silicon nitride (SiNx) films of various quality were deposited on the back‐side of a‐Si:H thin film transistors (TFTs) as a passivation layer. Although the films were not deposited directly on the channel region, the N/Si ratio of the film affected the TFT performance. It changed the threshold voltage and the subthreshold slope. In the linear region, the effect of the passivation layer was explained by assuming fixed charges in the nitride layer. Furthermore, the current‐voltage characteristics in the saturation region were explained by a parasitic TFT model. It was determined that a nitrogen rich passivation film is preferrable for liquid crystal displays.

Preparation of Pb(Zr, Ti)O3 Thin Films on Glass Substrates.

Lead-zirconate-titanate (PZT) thin films were prepared on non-alkaline glass substrates widely used in liquid crystal display (LCD) devices, by plasma-assisted magnetron RF sputtering with an immersed coil. After preparation of the PZT thin film, the glass was available for use in LCD device processing. No mutual diffusion of the elements was recognized between the glass substrate and the bottom electrode. The PZT layer had a dense film structure with rectangular and columnar grains, and only its perovskite phase was crystalline. PZT thin films on a glass substrate had leakage current densities of about 10-8 A/cm2, acceptable hysteresis loop shapes with the remanent polarization (Pr) of 45 µC/cm2 and the coercive field (Ec) of 90 kV/cm. Ferroelectric properties on a glass substrate almost conform with those on a Si-based substrate.

Preparation of Pb(Zr, Ti)O3 Thin Films by Plasma-Assisted Sputtering

A novel plasma-assisted RF magnetron sputtering system with an immersed coil antenna between a target and a substrate was applied for preparing Pb(Zr, Ti)O3 (PZT) thin films. The antenna enabled the generation of inductively coupled plasma (ICP) independently of the target RF source. The plasma assisted by the antenna resulted in the changes of ion fluxes and these energy distributions irradiating to the substrate. The crystalline phase of the deposited PZT thin films was occupied by the perovskite phase depending on the antenna power. In addition, a high deposition rate, modified uniformity of film thickness, and a dense film structure with large columnar grains were obtained as a result of effects of the assisted plasma. The application of the plasma-assisted sputtering method may enable the preparation of PZT thin films that have excellent properties.

Experimental Study for Evaluating Striae Structure of TiO2–SiO2 Glasses Using the Line-Focus-Beam Ultrasonic Material Characterization System

Striae configurations in TiO2–SiO2 ultra-low-expansion glasses caused by variations in TiO2 concentration were investigated through measurement of leaky surface acoustic wave (LSAW) velocities by the line-focus-beam (LFB) ultrasonic material characterization system. LSAW velocity distributions were measured on the surface of a specimen substrate prepared from a large circular plate glass ingot produced by the direct method using a flame hydrolysis process. A subsequent procedure that included polishing the surface of the specimen to reduce the specimen thickness by 40 µm and measuring the LSAW velocity distributions on the surface was repeated five times in order to examine at least one period of the striae. TiO2 concentration variations were clearly observed in the deposit direction of the glass ingot and in its radial direction. The maximum LSAW velocity difference over the whole examined region was 11.7 m/s, corresponding to 0.70 wt % TiO2 concentration. The three-dimensional striae structure revealed that the striae plane in the examined region was almost parallel to the substrate surface but gently curved down in the radial direction. The plane had a slightly convex-shaped cross section layered with a striae periodicity of about 0.16 mm and a curvature radius of about 440 mm, and also existed in a circular form with a curvature radius of about 450 mm. The ultrasonic method will contribute to improvement of characteristics and homogeneity of glass associated with production-process conditions.

Accurate Velocity Measurement of Periodic Striae of TiO2–SiO2 Glasses by the Line-Focus-Beam Ultrasonic Material-Characterization System

The evaluation of periodic striae layers in TiO2–SiO2 ultra-low-expansion glasses, formed during production, is discussed through the measurement of leaky surface acoustic-wave (LSAW) velocities by the line-focus-beam (LFB) ultrasonic material-characterization system. The averaging effect associated with an LSAW propagation region interacting with periodic striae on a specimen surface was examined at 225 MHz, taking several specimens prepared with inclination angles of θ=0, 2, 5, 10, 20, and 90° to the plane of striae layers with a periodicity of 0.16 mm. LSAW velocities corresponding to TiO2 concentrations in the glass were properly measured for the specimens with θ less than 10°, and the perpendicular specimen (θ=90°) was suitable for accurate determination of the striae periodicities for LSAW propagation perpendicular to the striae plane.

Semi-epitaxial bcc Ta Growth on Metal Nitride

The crystal structure change of sputtered Ta metal according to the nonmetal underlayer film was studied. The bcc-structure Ta was grown on TaNx, NbNx and bcc Mo underlayer films, whereas tetragonal-structure Ta was grown on glass, Ta2O5 and some metals. The crystal structure of Ta varied from tetragonal to bcc according to the N composition of the TaNx and NbNx underlayer films. The bcc Ta growth on TaNx was explained in terms of crystal structure compatibility of the Ta lattice arrangement between TaNx and bcc Ta, and tetragonal Ta growth on Ta2O5 film could be explained by partial Ta lattice matching between Ta2O5 and Ta crystals. Bcc Ta on the TaNx film gave a low resistivity of 25 µΩcm, in contrast to that of conventional tetragonal Ta of 180 µΩcm. The resistivity of Ta anodic oxide was increased by five orders of magnitude by adding N compared to that of conventional Ta anodic oxide. Low-resistivity bcc Ta on TaNx and high-resistivity TaN anodic oxide are applied as gate bus lines of TFT-LCD.

A Low‐Power, Image‐Memory LCD using Ferroelectric Film with Gray‐Scale Capability

A novel image-memory LCD using ferroelectric film for memory elements with gray-scale capability and ultra-low-power consumption has been proposed. We have demonstrated the operation of image-memory function by using an LC cell with discrete ferroelectric devices. A gray-scale image without any power consumption for more than several seconds has been obtained.

Intercalation of Cationic Porphyrin Bearing Four ω-Ammonioalkyl Subsutituents at Meso-Positions into Clay Montmorillonite, Saponite, and Hectorite

Abstract A novel cationic porphyrin bearing flexible ω-ammonioalkyl side chains, TMAP-Cl was prepared in high yield by using the K10 method. It was found that TMAP-Cl can be quantitatively ion-exchanged into interlamellar spaces of Mont, Sapo, and Hecto without suffering any protonation to the porphine ring. Especially, in the TMAP-Mont intercalation compound, the interlamellar distance was expanded to 10 A, which implies that a porphine ring in TMAP is installed upright rather than parallel to the clay surface.